In the fields of displays for use in television receivers and information terminals, studies have been made for replacing conventionally mainstream cathode ray tubes (CRT) with flat-panel displays which are to comply with demands for a decrease in thickness, a decrease in weight, a larger screen and a high fineness. Such flat panel displays include a liquid crystal display (LCD), an electroluminescence display (ELD), a plasma display panel (PDP) and a cold cathode field emission display (FED). Of these, a liquid crystal display is widely used as a display for an information terminal. For applying the liquid crystal display to a floor-type television receiver, however, it still has problems to be solved concerning a higher brightness and an increase in size. In contrast, a cold cathode field emission display uses cold cathode field emission devices (to be sometimes referred to as “field emission device” hereinafter) capable of emitting electrons from a solid into a vacuum on the basis of a quantum tunnel effect without relying on thermal excitation, and it is of great interest from the viewpoints of a high brightness and a low power consumption.
FIG. 22 shows a schematic partial end view of a cold cathode field emission display having field emission devices (to be sometimes referred to as “display” hereinafter). The field emission device shown in FIG. 22 is a so-called Spindt-type field emission device having a conical electron-emitting portion. Such a field emission device comprises a cathode electrode 11 formed on a supporting member 10 formed of a glass substrate, an insulating layer 12 formed on the supporting member 10 and the cathode electrode 11, a gate electrode 13 formed on the insulating layer 12, a first opening portion 14A formed through the gate electrode 13 and a second opening portion 14B formed through the insulating layer 12, and a conical electron-emitting portion 15 formed on the cathode electrode 11 positioned in the bottom portion of the second opening portion 14B. Generally, the cathode electrode 11 and the gate electrode 13 are formed in the form of a stripe, each stripe being oriented in directions in which the projection images of these two electrodes cross each other at right angles. Generally, a plurality of field emission devices are arranged in a region (corresponding to one pixel, and the region will be called an “overlap region” or an “electron-emitting region EA” hereinafter) where the projection images of the above two electrodes overlap. Further, generally, such electron-emitting regions EA are arranged in the form of a two-dimensional matrix within an effective field (which works as an actual display portion) of the cathode panel CP.
The anode panel AP comprises, for example, a substratum 20, a phosphor layer 23 (a phosphor layer 23R that emits light in red, a phosphor layer 23G that emits light in green and a phosphor layer 23B that emits light in blue in a case of a color display) which is formed on the substratum 20 and has a predetermined pattern, and an anode electrode 24 formed thereon. The anode electrode 24 has not only a function such as a reflecting film which reflects an emitted light from the phosphor layer 23, but also a function such as a reflecting film which reflects electrons recoiled from the phosphor layer 23 or secondary electrons emitted from the phosphor layer 23, and a function for preventing electrostatic charge of the phosphor layer 23.
Each pixel is constituted of an electron emitting region EA on the cathode panel side and a phosphor layer 23 on the anode panel side facing a group of these field emission devices. In the effective field, these pixels are arranged in the order of hundreds of thousands to several millions. A partition wall 322 is formed on the substratum 20 between one phosphor layer 23 and another phosphor layer 23. FIGS. 3 to 5 schematically show layouts of the partition wall 322, the spacer 331 and phosphor layer 23. Further, a light-absorbing layer (called “black matrix” as well) 21 is formed on the substratum 20 between one phosphor layer 23 and another phosphor layer 23. Part of the partition wall 322 works as a spacer holder 330. While FIGS. 3 to 5 show the partition wall 22, the spacer holder 30 and the spacer 31, the partition wall 22, the spacer holder 30 and the spacer 31 shall be read as the partition wall 322, the spacer holder 330 and the spacer 331.
A plurality of separation walls 322 prevent the occurrence of a so-called optical crosstalk (color mixing) that is caused when electrons recoiling from the phosphor layer 23 or secondary electrons emitted from the phosphor layer 23 enter another phosphor layer, or prevent the collision of electrons with another phosphor layer when electrons recoiling from the phosphor layer 23 or secondary electrons emitted from the phosphor layer 23 enter another phosphor layer 23 over the separation wall.
The anode panel AP and the cathode panel CP are arranged such that the electron-emitting regions and the phosphor layers 23 are opposed to each other, and the anode panel AP and the cathode panel CP are bonded to each other in their circumferential portions through a frame (not shown), whereby the display is produced. In an ineffective field which surrounds the effective field and where a peripheral circuit for selecting pixels is provided, a through-hole (not shown) for vacuuming is provided, and a tip tube (not shown) is connected to the through-hole and sealed after vacuuming. That is, a space surrounded by the anode panel AP, the cathode panel CP and the frame is in a vacuum state.
When the spacer 331 is not provided between the anode panel AP and the cathode panel CP, therefore, the display is damaged under and due to atmospheric pressure.
Therefore, in an image display or a flat-type display disclosed in JP-A-7-262939 or JP-A-2000-156181, a positioning member or a supporting member is formed on a black matrix formed on a front panel or a substrate, a brace member or a spacer is embedded between a pair of the positioning members or between the supporting members.
Further, in an image display disclosed in JP-A-2000-57979, a spacer and a cathode substrate are fixed to each other with an ultraviolet ray curing adhesive or an inorganic adhesive. Further, JP-A-10-199451 discloses a display in which a panel body and a spacer portion are integrated.
Meanwhile, the spacer 331 generally has a height of 1 to 2 mm and thickness of 0.05 to 0.1 mm. During the process of producing the display, therefore, it is difficult to keep the spacer 331 self-supported, and it is required to hold the spacer 331 between a pair of the spacer holders 330. For embedding the spacer 331 reliably between a pair of the spacer holders 330, the distance between the pair of the spacer holders 330 is required to be greater than the thickness of the spacer 331. When the distance between the pair of the spacer holders 330 is too broad as compared with the thickness of the spacer 331, however, the spacer 331 comes to tilt in the process of producing a display after the spacer 331 is embedded between the pair of spacers 330, and when the anode panel AP and the cathode panel CP are assembled, there is caused a problem that the spacer 331 and the spacer holder 330 are broken. Particularly, when the display is increased in size, the number of the spacers increases, and it is more difficult to hold the spacers perpendicularly.
In the image display disclosed in JP-A-2000-57979, the spacer and the cathode substrate are fixed to each other with an ultraviolet ray curable adhesive or an inorganic adhesive, so that the tilting of the spacer 331 can be prevented. However, there are remaining problems on the release of a gas from the adhesive and thermal deterioration of the adhesive. When a gas is released from the adhesive, the vacuum degree inside the image display may be degraded. When some gas is present inside the image display, for example, a cold cathode field emission display has problem that since fine electron emitting portions are sputtered with ions generated by the gas, the electron emission efficiency is changed, or that since electron emitting portions are damaged, the lifetime of the image display is decreased.
In the display disclosed in JP-A-10-199451, there is caused a problem wherein because the process for producing an integrated structure of a panel body and a spacer portion is difficult, the production cost is increased.
JP-A-2000-200543 discloses a technique of bonding circumferential portions of an anode panel and a cathode panel to each other with a low-melting metal. However, it describes nothing concerning the fixing of any spacer.
It is therefore an object of the present invention to provide a flat-type display having a structure that can avoid the occurrence of the problem in which the spacer tilts in the process of producing the flat-type display and that is free of the problems of the release of a gas from a material fixing the spacer and the thermal deterioration of a material fixing the spacer, and a method for producing the same.